CHAPTER VI. 



STRATIGRAPHICAL GEOLOGY. 



The Early Foundations of Stratigraphy. In the year 1762, } 

 Fiichsel proposed the term Formation for a series of strata / 

 accumulated under similar conditions and in immediate suc- 

 cession to one another. The expression was meant to indicate 

 not only the origin, but also a certain horizon in the strati- 

 graphical succession, and the particular geological age of the 

 series. By Werner's use of the term, it was given an essen- 

 tially petrographical significance, and lost Fiichsel's conception 

 of the serial succession of rock-deposits. In Werner's tea.ch- | 

 ing, the rocks of similar petrographical character were united 

 into a formation ; thus the sandstones were regarded as a 

 "formation" distinct from the limestones, and the limestones 

 represented a "formation" distinct from shales, porphyries, 

 etc. But as formations of sandstone, limestone, etc., re- 

 curred again and again in the rock-succession, Werner's system 

 allowed for this repetition by grouping the different petro- 

 graphical formations into " suites," and supposing each suite 

 to represent a definite period in the history of sedimentation. 



Brongniart and Cuvier, as well as most of their contem- 

 poraries in France, associated with the term Formation merely 

 the conception of a particular mode of origin and consequent 

 character of the deposit. On the other hand, for a complex \ 

 group of strata accumulated within a definite geological epoch, 

 the expression Terrain was suggested by Bonnard, Brong- 

 niart, and Prevost. In the works of De la Beche, the 

 term Group^ in Murchison's writings the term System, is 

 synonymous with Fiichsel's conception of Formation. 



Humboldt followed Werner in giving to the Formation 

 chiefly a genetic and petrographical significance, but he 

 assigned also a certain chronological value. He defined the 

 Formations as "Systems of mineralogical accumulations, which 



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